Mercury interrupter



Feb. 24, 1942. w. s. BRIAN 2,255,928

MERCURY INTERRUPTER Filed Jan. 20, 1959 l z'llz'am J. $432272 BB 751 w: (Ittomegs Patented Feb. 24, 1942 MERCURY INTERRUPTER William 8. Brian, Owensboro. Ky., assig'nor to General Motors Corporation, Detroit, Mich, a

corporation. of Delaware Application January 20, 1939, Serial No. 251,886

4 Claims. (Cl. 200-113) This application relates to interrupter means and more specifically to means for automatically interrupting a circuit supplied by a direct current a source in order to obtain pulsated D. C. for va ying the voltage and current ratios of the same.

There are various instances in which the only source of power available is direct current, more specifically in mobile units such as automobiles, ships or other instances where battery power alone is available. It is of course often necessary for various uses to provide diflerent voltages than that normally supplied by the battery or other D. C. source. Since direct current cannot be transformed in voltage it is necessary to interrupt the same so that transformation may take place and a higher or lower voltage applied to certain'deslred apparatus.

It is the object of my invention to provide an automatic interrupter for use in a direct current circuit.

It is a further object of my invention to provide a simple and substantially fool-proof interrupter which can be economically manufactured and will have long life.

With the above and other objects in view. my invention will be better understood by reference to the following specification and claims and illustrations in the accompanying drawing, in

which: a

Figure 1 shows a section through an interrupter embodying the features of my invention.

Figure 2 is a detailed enlarged view in perspective of the separating disk of Figure 1.

It has been found that when a certain amount of mercury has a portion of its cross section reduced to a substantially minute size and current passed therethrough that under certain circumstances if the current density is sufficiently high the mercury will vaporize. 01 course as soon as this vaporization takes place this portion of the circuit will no longer transmit current and the mercury may, if the attenuating circumstances are proper, recondense and again form the cir- I cult. This type of operation is clearly described in my pending application Serial No. 241,883, filed November 19, 1938, Patent #2,258,736 patented October 14, 1941.

In the present application there is illustrated a large outer envelope 2 which may be formed of glass or any other suitable substance. Near the center thereof there is a slight reduced section I within which is supported vertically across the axis of the tube a small disk 6 dividing the tube into two substantially equal chambers such as I and II, both being partially filled-with mercury i2, sufilcient to extend from the electrodes to the disk. Electrodes I4 and it are provided in opposite ends and adapted to contact the mercury pools in the two ends which may be connected to any desired source of current. v

The center disk I which is better shown in Figure 2 is of'the same shape as the cross section of the tube 2 and is formed of a material capable 'of withstanding high temperatures and being an electrical insulator such as for example ceramic material. This center disk has a counterbored portion ll and a small hole 20 drilled through the remainder of the disk, thus the two pools of mercury in the two opposite ends of the tube are separated by this ceramic disk and when the two electrodes i4 and it have current applied therethrough this current flows through the mercury in both pools and they are interconnected in series circuit by the amount of mercury in the small opening 20. As this is a very small opening the current density is high and therefore causes a vaporization of the mercury at this point which immediately recondenses and we have an automatic circuit interrupter. The ceramic disk is also utilized because the temperature rises and at this point is quite high and it is necessary to have some material which will withstand comparativeiy high temperatures. It is also neces- The particular compositions utilized have been steatite which has been fired and a material formed of a small amount of zircon with aluminum oxide. Thi latter disk was made of the following quantities of the two compositions which will serve as an illustration of satisfactory materials. It was prepared of 88% body and 12% resin, the body being formed of 5% zircon and A1203. The disks were'cold-pressed at 2 ton and then calcined, the h e then drilled therethrough and then fired a 1000 C., the size of the hole being anywhere from .002 to .005. The size of the hole of course depends to a large extent on the proposed curren -carrying capacity of the interrupter; The higher the capacity the larger the size of the hole necessary.

The reasons for having the disk substantially iacent the center of the tube and the mercury placed within the opposite ends and the tube sealed with the electrodes in contact with the mercuryportion and mercury extending through the opening to Join the two pools.

In order to increase the frequency oi operation of the interrupter it is desirable to assist in the condensation of the vapor bubble in the restriction. This may be done by causing the air in the end chambers to be under pressure or to entirely fill the end chambers with mercury so that the pressure on the bubble will be greater. The operation of the device may alsobe improved by putting in a small amount of some material to reduce the surface tension of the mercury, such as potassium in amounts from .05 to .25%.

I claim:

1. In an automatic periodic interrupter. an envelope, 3. ceramic disk supported within the envelope and dividing it into a plurality of chambers, said disk formed of a mixture 01' A120: and zircon to withstand heat and provide sufllcient mechanical strength, said disk having an aperture therethrough, mercury partially filling the chambers and flowing through the aperture, and means applying a potential difference to the large bodies of mercury causing current flow through the mercury in the aperture sufllcient to heat and vaporize the same to break the circuit which at once condenses and again reforms the circuit.

2. In a device for automatically periodically interrupting direct current comprising an envelope of insulating material, a disk forming a partition dividing the envelope into a plurality of chambers, said partition being an insulator of heat and electricity, and having an aperture,

of a cross sectional area substantially less than that or the envelope and a countersunk portion adjacent said aperture, a fluid having high electrical conductance partially filling said envelope and means for applying an electrical potential difference to the fluid in said chambers either side of said partition of a value sufficient to produce a current density in the portion 0! the fluid contained in the aperture of said partition to cause heating and vaporization of the fluid therein so that the current flowing therethrough will be periodically interrupted, said countersunk portion providing a short aperture while the additional thickness of the peripheral portion 01' the disk will give sufficient mechanical strength thereto.

3. In an automatic periodic interrupter, an insulating envelope, a disk of electrical and heat insulating material mounted within the envelope and dividing the same into two chambers, said disk having an aperture therethrough, a fluid or high electrical conductance partially filling both chambers, electrodes carried by each chamber and adapted to contact the fluid whereby current is conducted from one electrode to another through the fluid in the two chambers and the aperture to provide automatic'interruption thereof due to vaporization of the aperture fluid by high current density, and means added to the fluid to decrease the surface tension thereof to improve the interrupter operation.

4. In an automatic periodic circuit interrupter, a unitary insulating envelope, an electrical and heat insulating partition having an aperture therethrough supported within the envelope to divide the same into a plurality of chambers, an electrode sealed into the envelope in each chamher, and a quantity of mercury partially filling the chambers and filling the opening through the partition and contacting both electrodes, said ribbon oi mercury being or such dimensions that upon application of a predetermined voltage across the electrodes the current flow there- -through will be sufllcient to causevaporization 

